This invention relates to gear shifters for motorcycle transmissions, and more particularly to a device for a motorcycle transmission for automatically locating and positively engaging the transmission""s neutral position.
Typical motorcycle transmissions include a gear shifter mechanism including a shifter cam that is caused to rotate through predetermined rotational displacements for effecting gear shifts. Such shifter cam rotations are effected by the motorcycle operator""s foot operating a shifter lever coupled to the shifter cam for causing each gear to be sequentially engaged. Successively moving the foot operated shifter lever to the limit of its travel in one direction causes the transmission to shift into higher gears, while moving the lever to the limit of its travel in the other direction causes the transmission to be shifted into lower gears.
The conventional motorcycle transmission has a neutral position in which the rotational input from the engine is not transferred to the output shaft. Detents on the shifter cam are located at positions corresponding to the engagement positions of each gear and of neutral, and a spring-loaded plunger or other device bears against the appropriate detent for maintaining the shifter cam against further rotational movement after the shifter lever returns to its centered position. During a shift operation, a sufficient rotational force is applied to the shifter cam for rotating the shifter cam and for causing the spring-biased plunger to retract from its detent.
The neutral position of a motorcycle gear shifter is typically located between first and second gears and is not engageable at a cam position corresponding to any shifter lever limit of travel. Neutral may be selected by down-shifting the transmission from second gear but allowing the shifter lever to travel through only a portion of its arc. Similarly, neutral may be engaged by up-shifting from first gear and allowing the lever to travel through only a portion of its arc. In either case, the neutral position is determined by a change in the operator""s foot pressure for rotating the shifter cam to a position for permitting the neutral detent to be engaged by the spring-loaded plunger. In actual practice, the neutral position is often difficult to locate and engage, so that in attempting to shift into neutral from second gear an overshift frequently occurs resulting in first gear being engaged instead. Similarly, when attempting to shift into neutral from first gear, an overshift may occur resulting in second gear being engaged.
The difficulties in finding and positively engaging the neutral position of prior art motorcycle transmissions are avoided by the present invention, which provides an automatic neutral finder apparatus for causing the shifter cam to stop its rotation at the neutral position upon the motorcycle operator""s operation of a switch while down-shifting from second gear or up-shifting from first gear. The transmission""s spring-loaded gear-maintaining plunger is thereupon permitted to engage the cam""s neutral detent for maintaining the shifter cam in its neutral position until the next forward ratio gear shift is commenced by the operator.
In a motorcycle transmission according to the present invention, there is provided neutral finder apparatus operable by a motorcycle operator comprising in combination: a shifter cam rotatable about an axis through predetermined rotational displacements for effecting gear shifts and having a neutral position; a stop indexed to the neutral position of the cam; a plunger actuable for engaging the stop to stop rotation of the cam when the cam is at its neutral position; and a circuit associated with the plunger and including a switch operable by the motorcycle operator for actuating the plunger to engage the stop. The plunger is further actuable for disengaging the stop, and the switch may be operable by the motorcycle operator for actuating the plunger to disengage the stop. The circuit may include a lamp that is energized when the transmission is in neutral for signaling the motorcycle operator to operate the switch for actuating the plunger to disengage the stop.
The circuit preferably precludes actuation of the plunger to engage the stop unless the cam is rotated such that the plunger is positioned within a predetermined range of the stop. Where the neutral position is between two consecutive gear positions of the cam (such as between first gear and second gear), the circuit preferably precludes actuation of the plunger to engage the stop unless the cam is rotationally displaced within a range of rotational displacements between such two consecutive gear positions.